1. Field of the Invention
The present invention relates to foamed well cement slurries, additives for foaming the cement slurries and methods of using the slurries.
2. Description of the Prior Art
Hydraulic cement slurries are commonly utilized in subterranean well completion and remedial operations. For example, hydraulic cement slurries are used in primary cementing operations whereby strings of pipe such as casings and liners are cemented in well bores. In performing primary cementing, a hydraulic cement slurry is pumped into the annular space between the walls of a well bore and the exterior surfaces of a pipe string disposed therein. The cement slurry is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe in the well bore and bonds the exterior surfaces of the pipe to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
In carrying out primary cementing as well as remedial cementing operations in well bores, the cement slurries utilized must often be light weight to prevent excessive hydrostatic pressure from being exerted on subterranean formations penetrated by the well bore. As a result, a variety of light weight cement slurries have heretofore been developed and used including foamed cement slurries.
In addition to being light weight, a foamed cement slurry contains compressed gas which improves the ability of the slurry to maintain pressure and prevent the flow of formation fluids into and through the slurry during its transition time, i.e., the time during which the cement slurry changes from a true fluid to a hard set mass. Foamed cement slurries are also advantageous because they have low fluid loss properties.
While foamed cement slurries have included various surfactants known as foaming and foam stabilizing agents or additives for facilitating the foaming and stabilizing of cement slurries when a gas is mixed therewith, the heretofore used foaming and stabilizing additives have not met complete environmental requirements. That is, when the foaming and stabilizing additives find their way into water in the environment, they do not fully degrade which can result in interference with aquatic life cycles.
Thus, there are needs for improved foamed well cement slurries, improved cement slurry foaming and stabilizing additives which degrade completely in the environment and are totally harmless thereto and improved methods of utilizing the foamed well cement slurries.
The present invention provides improved foamed well cement slurries, improved foaming additives for foaming and stabilizing the cement slurries which are totally harmless to the environment and methods of using the improved foamed well cement slurries which meet the needs described above and overcome the deficiencies of the prior art. The improved foamed cement slurries are basically comprised of a hydraulic cement, sufficient water to form a pumpable slurry, sufficient gas to form a foam and an effective amount of an environment harmless additive for foaming and stabilizing the slurry comprised of hydrolyzed keratin.
The cement slurry foaming and stabilizing additive which is harmless to the environment is keratin which has been base hydrolyzed to form a protein powder. The additive is preferably pre-dissolved in water to form an aqueous solution which is added to the cement slurry along with a gas for foaming the slurry.
The methods of the present invention comprise the steps of forming a foamed cement slurry of the present invention comprised of hydraulic cement, sufficient water to form a pumpable slurry, sufficient gas to form a foam and an effective amount of the above described environmentally safe additive for foaming and stabilizing the cement slurry, placing the foamed cement slurry into a subterranean zone by way of a well bore penetrating the zone and then allowing the foamed cement slurry to set into a hard impermeable mass therein.
It is, therefore, a general object of the present invention to provide improved foamed well cement slurries, additives and methods.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.